syn

It is an abbreviation of the word synonym. e.g. "syn.bainesii" is telling you that Aloe barberae was once known as Aloe bainesii.

sp

It is an abbreviation of the word species. Aloe sp. means an Aloe of as-yet-unknown identity. Note that species is singular, there is no such thing as a specie!　

ssp　

It is an abbreviation of the word subspecies. A subspecies is a lesser rank within a species.

spp　

spec.　

It is an abbreviation of the word specimen. Meaning an example of, or sometimes used to mean an excellent example of, as in Coro Cacti's Website Specimens page.　

cf.　

It stands for 'compare with'. Aloe cf. ferox means an Aloe that is possibly within Aloe ferox or else is closely related.　

aff.　

It stands for 'has an affinity with'. e.g. Aloe aff. ferox means an Aloe that is closely related to Aloe ferox, but is of an as yet undetermined or undescribed identity.　

'English Words'　

When we see appended to the genus or species name some English words (not Latin) with single quotes around them as in Genus species 'English Words' it tells us that the plant is a named hybrid or cultivar (cv.). For these names Latin is not allowable. Sometimes they are formally described by botanists in prestigious journals (e.g. Tavarorbea 'Red Leopard' by Dr. Colin Walker in New Zealand Cactus and Succulent Journal) and sometimes they are informally named by nurseries, breeders, or hobbyists (as in Gasteraloe 'Green Hysteria' named during NZ's great GM debate of 2003). 　

HS 151　

You will often see combinations of initials with numbers after the botanical name. This is called the 'Collection Number'. The initials are usually those of a botanical explorer and the number is taken originally from his field notes. It denotes a specific wild population of plants from which seeds or plant material was collected, usually from a small area like a part of a hillside. Ralph Martin's website, http://ralph.cs.cf.ac.uk/Cacti/fieldno.html is excellent for checking locality details as well as the latest identity of that population. Sometimes the plant collection initially has no name, just the Collection Number, and only years later it might be formally described..... ..after which Ralph baby will see you right. Plants with Collection Number data are, to the serious collector, of higher value. They have a greater botanical significance. The Collection Number can also be used to identify particularly attractive or interesting populations. HS 151 is, in fact, a very choice Sulcorebutia collected at Siles, between Totora and Omereque, Cochabamba, Bolivia, by Heinz Swoboda and only named nearly 20 years later as Sulcorebutia heinzii.　

inflorescence

It is the name given to the structure emanating from a plant which bears the flowers. If two emanate then there are two inflorescences.

raceme

It is the name given to the bunch of flowers. There can be many flowers on a raceme. There can be many racemes on an inflorescence.

caudex

It is the swollen lump at about ground level which stores water in enlarged succulent cells. Plants with this feature are called caudiciforms, or Lump Plants. They often, but not always, have an annual vining upper growth with non-succulent leaves.

pachycaul

It is a plant with extra thick stems and sometimes thick branches too. These stems store water in enlarged succulent cells. The word comes from the Greek for "thick stem". These plants were until quite recently lumped in with caudiciforms, which have a more discrete caudex or 'lump'. Both caudiciforms and pachycauls are also affectionately known as fatties, or Fat Plants. Check out Yahoo Group Fat Plants, a very keen group of worldwide enthusiasts.

taxon and taxa

A taxon is "a taxonomic entity", and taxa is the plural of taxon. If you have in your collection a Lithops aucampiae and three different subspecies of Lithops lesliei, then you have just two species but you have four taxa. If you have 10 different specimens of Lithops aucampiae as well as your three types of L.lesliei then you still have only four taxa.